Outer race member for roller type one-way clutch

ABSTRACT

An outer race member for a roller type one-way clutch, includes a plurality of pawls provided along an outer periphery and engaging with an opposite member, a cam surface formed on an inner periphery, and grooves, formed in the inner periphery, for disposing block bearings. A radial width of a peripheral portion of the groove is formed larger than a radial width of other portion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an outer race member of a roller typeone-way clutch that is employed for an automatic transmission, etc.,wherein engagement members are interposed between an inner race memberand the outer race member.

2. Related Background Art

A roller type one-way clutch classified as one type of one-way clutchhas a construction that rollers defined as engagement members arepressed against and thus engaged with a cam surface formed on an innerperipheral surface of an outer race member or on an outer peripheralsurface of an inner race member, thereby locking rotation in onedirection.

FIG. 5 is a partially exploded front view of this roller type one-wayclutch in the prior art. A roller type one-way clutch 30 is constructedof an inner race 32 as a solid shaft member and an outer race 33 intowhich the inner race 32 is fitted. The outer race member, i.e., theouter race 33 is formed, on its outer peripheral surface, with pawls 38engaging with an unillustrated opposite member.

Block bearings 37, rollers 36 and springs 35 for biasing the rollers 36in an engaging direction, are disposed between the inner race 32 and theouter race 33. The outer race 33 has a cam surface on its innerperipheral surface, and the rollers 36 engage with this cam surface,thereby locking the rotations.

Provided further between the outer race 33 and the inner race 32 are thesprings 35 and the rollers 36 that constitute a torque transmissionmechanism, and also cages 34 for holding the rollers 36. The blockbearing 37 effects positioning of the cage 34 with respect to the outerrace 33.

The roller type one-way clutch might suffer a fatigue failureoriginating from a groove for disposing the block bearing due torepetitive free/lock operations. Therefore, a thickness of the outerrace in a radial direction becomes larger for ensuring a sufficientstrength.

While on the other hand, however, a decrease in weight is demanded ofthe roller type one-way clutch as a whole. It is therefore desired thatthe two requests in terms of the strength and the decrease in weight bemet simultaneously.

A clutch known as the roller type one-way clutch described above isdisclosed in Japanese Patent Application Laid-Open No. 11-051091. Thisdocument teaches that a weight of the whole one-way clutch is reduced byintegrally forming the cages by use of plastic.

As disclosed in Japanese Patent Application Laid-Open No. 11-051091,however, if the cages are formed of the plastic, though this cancontribute to reduce the weight, there still remains a problem in termsof the strength. Further, even when reducing the weights of the cagesthat are not essentially so heavy, there is still the problem in whichthe weight reduction of the cages does not sufficiently contribute todecrease the weight of the whole one-way-clutch because of a heavyweight of the outer race member, etc.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide anouter race member for a roller type one-way clutch that is capable ofimproving durability against repetitive free/lock operations whilereducing a weight thereof.

To accomplish the above object, an outer race member for a roller typeone-way clutch according to the present invention includes a pluralityof pawls provided along an outer periphery and engaging with an oppositemember, a cam surface formed on an inner periphery, and grooves, formedin the inner periphery, for disposing block bearings, wherein a radialwidth of a peripheral portion of the groove is formed larger than aradial width of other portion.

The peripheral portion of the groove in which the block bearing isdisposed, is formed thicker in wall than other portion, thereby makingit possible to acquire the outer race member capable of obtaining anecessary strength and attaining a reduction in weight.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially exploded front view of a one-way clutch includingan outer race member of the present invention;

FIG. 2 is a sectional view taken along the line 2-2 in an axialdirection in FIG. 1;

FIG. 3 is a front view showing an outer race member in a firstembodiment;

FIG. 4 is a front view showing an outer race member in a secondembodiment; and

FIG. 5 is a partially exploded front view of a roller type one-wayclutch in the prior art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will hereinafter be respectivelydescribed in depth with reference to the accompanying drawings. Itshould be noted that the same components are marked with the samenumerals throughout the drawings.

FIG. 1 is a partially exploded front view of a one-way clutch includingan outer race member according to the present invention. FIG. 2 is asectional view taken along the line 2-2 in an axial direction in FIG. 1.A roller type one-way clutch 10 is constructed of an inner race memberas a solid shaft member, i.e., an inner race 2, and of an outer racemember, viz., an outer race 3, taking substantially an annular shape,into which the inner race 2 is fitted on its inner diametric side. Theouter race 3 has a plurality of pawls 8 provided at equal intervals in aperipheral direction on an outer peripheral surface thereof, and engagesthrough these pawls with an unillustrated opposite member.

Block bearings 7, rollers 6 and springs 5 for biasing the rollers 6 inan engaging direction, are disposed between the inner race 2 and theouter race 3. The outer race 3 has a configuration, wherein a camsurface 11 (see FIG. 3) is provided on its inner peripheral surface, andthe rollers 6 engage with this cam surface 11, thereby locking therotations.

Provided further between the outer race 3 and the inner race 2 are therollers 6 and the springs 5 constitute a torque transmission mechanism,and also cages 4 for holding the rollers 6. The block bearing 7 effectspositioning of the cage 4 with respect to the outer race 3, and has abearing function.

The rollers 6, the springs 5 and the block bearings 7 are, as shown inFIG. 1, provided by pluralities in the peripheral direction. Threepieces of rollers 6 and three pieces of springs 5 are provided betweenthe block bearings 7 disposed at the equal interval in the peripheraldirection.

The block bearings 7 are assembled in from window portions (not shown)formed in cages 4, and upper portions of the bearings 7 are fitted in aplurality of disposition grooves 12 formed in an inner peripheralsurface of the outer race 3, thus effecting positioning of the blockbearings 7. Moreover, lower portions of the block bearings 7 are caughtbetween protrusions 4 c provided along peripheries of the windowportions and protruding outwards in the radial direction, and are thusset in a fixed state, thereby positioning the block bearings 7 in theperipheral direction.

As shown in FIG. 2, the cage 4 includes a flange portion 4 b on one sideend surface in the axial direction, this flange portion 4 b takingsubstantially an annular shape and extending outwards in the radialdirection. The cage 4 is held by the outer race 3 through this flangeportion 4 b . The other side end of the cage 4 in the axial directionabuts on a side end surface of the outer race 3 in the axial direction.

First Embodiment

The outer race member in a first embodiment of the present inventionwill hereinafter be explained in detail. FIG. 3 is a front view showingthe outer race member 3 in the first embodiment. A basic configurationof the outer race member 3 is as explained above. As can be understoodfrom FIG. 3, a radial width (thickness) T₁ of a contiguous portion 15 ofthe disposition groove 12 in the peripheral direction in a sectionbetween the adjacent pawls 8, 8 at an outer diametric portion of thedisposition groove 12 wherein the upper portion of the block bearing 7is disposed, is formed larger than other portion.

On the other hand, a portion 16 having no existence of the dispositiongroove 12, provided with the cam surface 11 and contiguous to the camsurface 11, has a radial width T2 and is smallest in thicknessthroughout the outer race member 3. A strength is improved by increasingthe wall thickness of the portion peripheral to the disposition groove12 where the fatigue failure is easy to occur, whereas there isdecreased the wall thickness of a portion peripheral to the cam surface11 of which the strength is not required so much, thereby enabling theweight of the outer race member 3 to be reduced.

Although a relationship such as T₁>T₂ is established, the width T₁ maybe the same as the radial width of the conventional outer race member,and a reduction in weight of the whole outer race member 3 can beattained by reducing the width T₂ relative to the width T₁.

Second Embodiment

Next, a second embodiment of the present invention will be explained.FIG. 4 is a front view showing an outer race member in the secondembodiment. As obvious from FIG. 4, according to the second embodiment,the pawls 8, 8 are disposed at unequal, i.e., narrow and wide intervals.Then, the block bearing disposing portion 12 (groove portion) is formedon the inner diametric side in a wide section between the pawls 8, 8.Pitches of the wide section and of the narrow section are setrespectively at 48° and 24° as central angles.

With respect to such an outer race 23 also, as in the second embodimentdiscussed above, if the wall thickness is set large throughout thesections between the pawls 8, 8, a reducible quantity of the weightbecomes small. Therefore, as in the second embodiment, with respect tothe outer race 23 having the wide section between the pawls 8, 8, a wallthickness not of the entire section between the pawls 8, 8 but of aperipheral portion 14 is set large at the center of an outer diametricportion of the block bearing disposing portion 12.

The wall thickness, i.e., a radial width T₃ of the peripheral portion 14is larger than a radial width of an area provided with none of the blockbearing disposing portion 12. A peripheral width of the peripheralportion 14 at the center of the block bearing disposing portion 12, islarger than a peripheral width of the block bearing disposing portion12.

The peripheral portion 14 is provided to encompass the block bearingdisposing portion 12 where the fatigue failure is easy to occur, therebymaking it possible to ensure a strength of the block bearing disposingportion 12 especially requiring a sufficient strength.

Table 1 shows a result of a comparative test for mass and durabilitybetween the outer race member in the second embodiment of the presentinvention and the conventional outer race member. Note that a testcondition is given as follows.

-   -   Test condition: Transmission torque 500N·m

Work specifications: Outer diameter; approximately φ130 mm (pawl portion142 mm) Inner diameter; approximately φ118 mm Thickness; approximately12 mm Rollers; 15 pieces Block bearings; 5 pieces Pawls; totally 10portions (alternate wide-and-narrow pitches . . . wide pitch 48°, narrowpitch 24°) TABLE 1 Mass of Outer Race Durable Life-Time Embodiment 340 gAbout 1000000 Cycles Comparative 359 g About 1000000 Example Cycles

As apparent from Table 1, according to the second embodiment of thepresent invention, the mass is decreased by 19 g, thus attaining thereduction in weight. Nevertheless, the same durability is acquired.

The present invention, which has been discussed so far, can be changedin a variety of forms. For example, the rollers and the springs aredisposed by threes between the block bearings 7 in FIG. 1 and can bealso, as a matter of course, provided by a number of pieces other thanthrees. Namely, each of the numbers of the rollers and the springs canbe set smaller or larger than three.

Moreover, according to the second embodiment, the pitches of the widesection and of the narrow section between the pawls 8, 8 are setrespectively at 48° and 24° as the central angles, however, other sizes(central angles) can be, as a matter of course, set.

According to the present invention discussed so far, it is feasible toprovide the outer race member of the roller type one-way clutch that iscapable of improving the durability against the repetitive free/lockoperations while reducing the weight.

1. An outer race member for a roller type one-way clutch, comprising: aplurality of pawls provided along an outer periphery and engaging withan opposite member; a cam surface formed on an inner periphery; andgrooves, formed in the inner periphery, for disposing block bearings,wherein a radial width of a peripheral portion of said groove is formedlarger than a radial width of other portion.
 2. An outer race member fora roller type one-way clutch according to claim 1, wherein theperipheral portion is provided between said pawls disposed apredetermined pitch.
 3. An outer race member for a roller type one-wayclutch according to claim 1, wherein the portion having the large widthis the peripheral portion of said groove and an entire section betweensaid pawls.
 4. An outer race member for a roller type one-way clutchaccording to claim 2, wherein the portion having the large width is theperipheral portion of said groove and an entire section between saidpawls.